1. Field of the Invention
This invention relates generally to a process for removing inorganic, organic, and microbiological contaminants from fluids. In its more particular aspects, the invention relates to the field of such devices that use ion exchange resins as one stage of a fluid treatment process. More particularly, a process for removing soluble and insoluble inorganic, organic, and microbiological contaminants from a fluid stream employing a pretreatment module, a post-treatment module, a recharging solution treatment module, and an ion exchange resin module, is provided. The process provided reduces the problems associated with ion-exchange resin fouling and increases contaminant removal capacity.
2. Description of Related Art
Purification of Water
Purification or filtration of water or other aqueous solutions is necessary for many applications, from the provision of safe or potable drinking water to biotechnology applications including fermentation processing and separation of components from biological fluids, and to industrial processes that require waste stream treatment and recovery of process chemicals. Similarly, the removal of contaminants from fluids used in medical procedures and semiconductor fabrication processes, where ultrapurified fluids are required, and in environments where the fluids will be recirculated, such as aircraft or spacecraft, is also an important application for filtration and fluid treatment materials. In recent years, the need for water filtration and purification in the home has become more recognized, and the competing concerns of energy efficiency and residential fluid quality have lead to numerous filtration products, that purport to remove small particles, allergens, microorganisms, intentionally introduced biotoxins, pesticides, and toxic metals such as lead, mercury, and arsenic.
There are many well-known methods currently used for water purification, such as reverse osmosis, distillation, ion-exchange, chemical adsorption, coagulation, and filtering or retention. Particle filtration may be completed through the use of membranes or layers of granular materials. Other fluid purification techniques involve chemical introduction which alters the state or chemical identity of the contaminant. Examples of chemical additives include oxidizing agents, flocculating agents, and precipitation agents.
In many fluid purification applications a combination of techniques are required in order to completely purify fluids, such as water. Combinations of technologies may be implemented by combining functions in a single device or using several different devices and technologies in series where each performs a distinct function. Examples of this practice include the use of mixed ion-exchange resins that remove both negative and positively charged chemical species and oxidation/filtration methods where oxidizers are used to generate particulate matter that may be subsequently filtered.
The use of ion exchange materials, namely naturally occurring minerals and synthetic minerals and resins in fluid treatment operations has become wide spread in the field. Ion exchange systems are currently commercially available in small volume formats such as pitchers, in larger residential volume formats such as whole house water softeners which remove hardness ions, and in specialty water purification systems that must remove contaminants that pass through reverse osmosis membranes. Ion exchange resins are also used in many industrial applications to remove or isolate important chemical and biological compounds and to remove contaminants. Ion exchange resin systems can be scaled significantly to handle very large volume applications. In practical potable water applications the ion exchange material must be recharged and reused to be cost effective. Recharging may be conducted with salt and/or acidic or basic solutions.
Ion exchange materials are available in two formats; one format removes positively charged ions by using a negatively charged material surface and the other format removes negatively charged ions by using a positively charged material surface. The ion-exchange surface in both formats may be tuned to increase the strength of the ion interactions. Although it is possible to increase the specificity of the material surface for specific ions this is generally not the case in commonly used materials. As a result, ion exchange materials remove ions at levels related to the ion charge and the relative concentration of all charged species in solution.
It is well understood that ion exchange water treatment systems have serious limitations when compared to other treatment systems and that the technology does not meet the requirements of many applications. Some of these drawbacks include the fouling of the ion-exchange material surface with organics and microorganisms, the plugging of the housings holding the particulate material, cost effectiveness, the limited capacity for ion removal and thus the need to regenerate the material, and the inability to remove uncharged contaminants from fluid streams. As a result, many applications require the coupling of additional technology with ion-exchange systems including reverse osmosis and other membrane systems.
There is significant prior art in the field of water treatment systems employing ion exchange materials. Specifically, there is significant art associated with the manufacture of ion-exchange materials including resins and zeolites, pH adjustment of “raw” fluids through chemical injection before material contact, the cleaning and recharging of ion exchange systems, the back flushing of ion exchange systems, and the design of automated and semi-automated treatment systems employing many variations of these procedures. Unfortunately, these modifications to the basic concept of pressurizing fluid against the ion exchange material and collecting treated fluid from the low-pressure side of the ion exchange material system does not address the organic, inorganic, and microorganism fouling that occurs on the ion exchange surface or the ability to remove uncharged contaminants from the fluid stream.
Accordingly one object of this invention is to provide an ion exchange based water treatment system which employs inexpensive, safe, and reliable ion exchange pretreatment, post-treatment, and recharge solution fluid conditioning. The process of the invention also serves to protect the ion exchange material from, particulates, chemical and microbiological contaminants, and to improve the removal level of some contaminants, all of which are objects of the invention. As a result many water treatment systems comprised of ion-exchange materials will be more applicable for residential point-of-use, point-of-entry applications, and increasing many industries.